“How old are you?” someone asks. Number of years since birth is the generally the answer – that is your Chronological Ageor CA.

But how hold do you feel? How old do you act? How old do you look? That is your Biological Age or BA.

Wouldn’t it be nice to actually be able to measure your biological age?

CA and BA is the difference between being 40 year old and going on 60. Or, may be being 60 year old and going on 40.

Wouldn’t it be more useful to have a single number like BA, than understanding individual factors like your total cholesterol, HDL, A1c, VO2 Max, etc?

Recently, in the media there has been a buzz about a recent research published by scientists led by Duke University School of Medicine about measuring biological age. For example, see the article in WSJ: How Quickly Are You Growing Old?

Now there are a quite a few websites, where you answer a bunch of question and they will tell you, your biological age as compared to your chronological age.

For example, here are three such sites, I tried (my CA is 60.9 years):

Each of the sites followed up with advice and helpful hints on what I could start or stop doing to further increase my expected health and lifespan.

Unfortunately, none of these websites show exactly what they do with the information you provide and how they arrive at the number they call Biological Age.

But this recent study, “Quantification of biological aging in young adults”, by Daniel W. Belsky et al,is very rigorous treatment of this subject and gives you all the details behind the curtain. And, for me, these details are not only fascinating but actually quite useful to understand what matters for biological age to start diverging from chronological age. In other words, what slows down or speed up aging.

The study calculated the aging rate of 954 men and women—taking various measurements of their bodies’ health—when they were each 26, 32 and 38 in chronological years. By analyzing how these measures changed over time, the researchers were able to see who aged faster and who slower than normal.

To measure the pace of biological aging, which the study defined as the declining integrity of multiple organ systems, the researchers relied on 18 separate biomarkers, summarized in figure below.

These ranged from common measures such as HDL-cholesterol levels and mean arterial blood pressure to more obscure ones like the length of telomeres—the protective caps on the ends of chromosomes that shorten with age.

Chronological age of all participants was 38 years. However, researchers found that the biological ages varied from 26 years to 60 years.

For measuring how fast people aged, they calculated aging over 12 years. About 30 percent aged biologically one year for every calendar year. There were those who aged as much as 3 years for every calendar year. And, there were four members of the group who aged not at all or actually got biologically younger during the 12 year period.

BOTTOMLINE:

Finding one’s Biological Age is a fascinating concept and can be very useful in optimizing health and life span. However, this is not an exact science just yet, although good strides are being made in research.

However, if you want to focus on living optimally, you can focus on changing your lifestyle to optimize the basic 18 or so biomarkers used in this study. Most of these can be impacted by lifestyle choices. Only 20% depend upon genetics.

“As an optimist, when I look at this data, it looks very encouraging to me. First, it is definitely viable to live to 120. It has already been done! Like the four-minute mile, someone has already shown the way.

Second, an increasing number of people are approaching that age with an increasing rate. So, at this rate, I expect by the time my time arrives, dying at 120 will be as routine as dying at 100 today! It might not be very common, but it might not be that rare.”

While I make this informal and what seems like a rather obvious deduction from the data, some folks disagree.

So, intuitively, the chart below may be how one would be tempted to guess the shape of life expectancy curves.

However, they argue, that it is the chart below that corresponds to the reality.

Thus according to their conclusion, while on an average humans are living longer and longer, we are still stuck at dying by the age of 100.

Presenting the data from another perspective in the chart below, as we graph number of deaths against age of death, we observe a normal or Gaussian distribution around certain age at which number of deaths peak. As the life expectancy keeps increasing the curve would look like the IDEAL curve below.

And, as that happens, graph of percent survial rate against age will become “rectanguar” as shown below.

This implies that as we conquer chronic diseases, we will live a healthy long life after which we will succumb very quickly to the forces of nature, within the bounds of a very few years. And, that will define an ideal “natural” death. As we hit certain time limit, all of the cells in the body may burst together like soap bubbles.

Fries and Crapo wrote their book in 1981. So I thought, with all the new research in the last 30+ years, maybe they have changed their mind.

I really like most everything else they assert, derive or conclude in that book- which I would like to talk about in a different post. However, I am personally not sold on this idea of fixed life-span.

It makes me quite uncomfortable. Yeah, you guessed it. After all, my goal is to purposely live to 120!

What do you think?

Have you seen any data, studies or analysis that contradicts this theory about fixed life-span?